Superheated steam has many commercial, industrial and consumer applications. It is important in power and energy generation and may be employed in production processes including surface preparation and treatment. Superheated steam has also proved to be effective in the control, removal and destructions of unwanted microorganisms and common household pests.
Commonly, in the prior art, steam is produced in a boiler or other vessel at high pressures. If desired, this steam at elevated pressure is further heated by various means to achieve a superheated state (above 100° C.). In many cases the combustion of fuels is employed to heat the water with an open flame boiler and produce steam. This combustion creates carbon monoxide and other pollutants. The heat produced by combustion, solar or nuclear processes is often converted to work energy via steam production. Use of these types of systems would be limited to open and unconfined areas and may require filtering means for any exhaust.
The prior art contains examples which disclose devices utilizing steam, sometimes superheated, to destroy insects and various other pests. U.S. Pat. No. 7,797,878 to Schuster (2010) presents a device to suppress fire ants utilizing the injection of superheated steam into an ant colony. This invention has several limitations. It is heavy, bulky and relies upon a handcart for ease of movement. The generation of superheated steam employs a complicated system to create steam and then reheat it to a superheated state. This invention only performs its intended purpose when a probe is driven into the ground to reach insects.
Likewise, U.S. patent application Ser. No. 12/757,969, published as 2011/0041782, by Vaughan presents a device to control pests and weeds utilizing steam, sometimes superheated, and hot air. This system is bulky and requires a cart with wheels for transportation. It is not compact and its usage in tight areas would be very limited. The system is complicated, needing a burner to heat water into steam, an electric blower to move the air and a means to pump the needed water. Also, instant steam is not produced.
U.S. Pat. No. 5,867,935 (1999) and U.S. Pat. No. 5,848,492 (1998), both to Brown, present an invention intended to apply superheated steam in agricultural applications to defoliate and to eliminate insect pests. This apparatus is large and very heavy. One embodiment is equipped with wheels in order that it may be pulled by a tractor or other means into position. It can only be utilized outdoors or where there is plenty of space. Indoor use is limited, if at all possible, in most situations. The system used for the heating and the projection of the steam is also complicated and does not produce instant steam.
U.S. Pat. No. 5,378,086 to Campbell, Jr. (1995) can utilize superheated steam, but is not portable. Rather, it is a permanent underground system for pest extermination. U.S. Pat. No. 4,620,388 (1986) and U.S. Pat. No. 4,716,676 (1988), both to Imagawa, are large stationary systems for the elimination of pests on, or in, fruit such fruit being placed inside of the invention. These three inventions have very limited, specific and non-portable intended applications and teach away from instant superheated steam.
U.S. Pat. No. 4,756,118 to Evans, II (1988) has a handheld applicator, but has a fuel and gas source that both are external to the applicator making it bulky and complicated. Gas is vaporized by a flame and then injected into fire ant colony. It is not intended to be used in any other manner, thereby limiting possible applications. Also, pure steam is not produced with the steam containing other gases as well.
U.S. Pat. No. 4,637,161 to Turner (1987) and U.S. Pat. No. 7,752,802 to McDonald (2010) are intended for underground elimination of ants and must be set up, inserted in the ground and used in place. They are thus not handheld and are limited in their usage.
U.S. Pat. No. 7,155,117 to Leung et al. (2006), U.S. Pat. No. 3,695,066 to Doyel (1972) and U.S. application Ser. No. 12/341,614 published as 2009/0313767 by Tanner et al. are handheld steam generators designed generally for the removal of wrinkles from fabric or clothing. Each is fairly complicated, either electronically or mechanically, and none is designed to produce superheated steam. These inventions are meant to be in close physical contact with a work-piece and will not function effectively if not. Usefulness for other purposes is thereby greatly diminished.
Steam is produced in boilers for mechanical work production. A boiler operates on the Psat−Tsat equilibrium principle. Rapid heat-up and rapid turn-off are not associated with boilers especially when high powers are desired. On account of the Psat−Tsat limits of boilers, the controllability of them is very low.
There is a need for an efficient, effective and instant electrically powered superheated steam generation system that performs this function without a conventional boiler at atmospheric temperature. An apparatus of this type would be safer, cleaner, greener, faster, less expensive and more efficient that current steam generation equipment and methods. Table 1 is a comparison of expected differences between boiler steam and superheated steam (please see http://www.mhi-inc.com/oab-superheated-steam-generator.html).